Visual comfort: stereoscopic objects moving in the horizontal and mid-sagittal planes

Two experiments were conducted to examine the visual comfort of stereoscopic images. The test video sequences consisted of moving meteorite-like objects against a blue sky background. In the first experiment, a panel of viewers rated stereoscopic sequences in which the objects moved back and forth in depth. The velocity of movement, disparity (depth) range, and disparity type (i.e., depth position with respect to the screen plane: front, behind, or front/behind) of the objects varied across sequences. In the second experiment, the same viewers rated stereoscopic test sequences in which the target objects moved horizontally across the screen. Also in this case, the velocity, disparity magnitude, and disparity type of the objects varied across sequences. For motion in the depth direction, the results indicate that visual comfort is significantly influenced by the velocity, disparity range, and disparity type of the moving objects. We also found significant interactions between velocity and disparity type and between disparity type and disparity range. For motion across the screen in the horizontal plane, ratings of visual comfort depended on velocity and disparity magnitude. The results also indicate a significant interaction between velocity and disparity. In general, the overall results confirm that changes in disparity of stereoscopic images over time are a significant contributor to visual discomfort. Interestingly, the detrimental effect of object velocity on visual comfort are manifested even when the changes are confined within the generally accepted visual comfort zone of less than 60 arc minutes of horizontal disparity.